The present invention relates to braking systems and, more specifically, to a spring-applied braking system with an electromagnetic release mechanism.
Braking systems have been around for many years and are used in various types of devices for stopping or slowing down a moving component. Probably one of the best known braking systems is a caliper-type braking system used on car brakes. The system typically includes two brake pads positioned on opposite sides of a rotating disc. The disc is slowed or stopped by hydraulically driving the brake pads toward the disc until they contact it. This type of hydraulic caliper disc system has been around for decades. One conventional caliper-type disc brake that can be used in an elevator is disclosed in U.S. Pat. No. 5,101,939.
Another type of conventional braking system uses an electromagnetic brake for stopping or slowing down a disc or rail. In this type of brake, electromagnetic energy is used to stop the rotating or moving component. One type of conventional of braking system that uses an electromagnetic brake is disclosed in U.S. Pat. No. 5,186,286. A disc brake using electromagnetic force in an elevator is disclosed in U.S. Pat. No. 5,154,261.
Most conventional braking systems must be physically activated or actuated in order to produce braking. For example, in a car disc brake, the brake is not automatically applied while the car is in motion. Instead, the brake is manually engaged when it is desired to stop the car by applying pressure to the brake pedal. There are, however, applications where it is advantageous or necessary for the brake be engaged by default. One example is an elevator. Due to safety concerns, it is advantageous that the brake is applied by default at all times. In these types of braking systems, in order to move the elevator car the brake must first be disengaged, thus assuring that a system failure automatically stops the elevator.
While there have been many braking systems developed over the years, a need still exists for an improved system which is relatively inexpensive to manufacture and provides quick and reliable braking in the event of a power failure.
The present invention relates to an electromagnetic brake system for controlling motion of a component that is movable relative to the brake system. The brake system includes a magnet body mounted to a support. The magnet body has at least one electrically controlled magnetic device mounted to it which is adapted to generate a magnetic force when activated.
A back plate is mounted adjacent to the magnet body and positioned on one side of a movable component. The back plate preferably includes a brake shoe positioned adjacent to the movable component.
An armature plate is located adjacent to the magnet body and positioned between the magnet body and the movable component. The armature plate is movable relative to the magnet body. A brake shoe is located on the armature plate facing the movable component.
At least one spring is located on the magnet body between the magnet body and the armature plate for biasing the armature plate away from the magnet body. The spring has a spring force that is less than the magnetic force generated by the magnetic device such that activation of the magnetic device moves the armature plate toward the magnet body overcoming the spring force.
A manual release mechanism is preferably mounted to the magnet body for manually controlling the translation of the armature plate toward the magnet body.
In one embodiment of the invention, the magnetic force is varied to reduce the force applied to the armature plate when the brake is released. This is achieved in one configuration by using multiple coils and turning off at least one when the brake is released. In another configuration the current supplied to the coil is varied to control the resulting magnetic force.
Preferably the magnet body and back plate are pivotally mounted to the support such that these components can be pivoted away from the movable component to permit maintenance.
The foregoing and other features and advantages of the present invention will become more apparent in light of the following detailed description of the preferred embodiments thereof, as illustrated in the accompanying figures. As will be realized, the invention is capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and the description are to be regarded as illustrative in nature, and not as restrictive.